Phase I, open-label, multidose study to administer rBPI21 intravenously to patients with cystic fibrosis, using three different regimens. Cystic fibrosis patients have pathology and morbidity associated with chronic gram-negative pulmonary infections and have been shown to have elevated levels of bacterial endotoxin when experiencing bacterial exacerbations. For these reasons, rBPI21 (recombinant bactericidal/permeability increasing protein is a 21kD recombinant human protein) has been proposed as a potential agent in treating cystic fibrosis, particularly those patients with multiple drug resistant Pseudomonas infections. Primary Objective: to assess safety, pharmacokinetics, and immunogenicity of rBPI21. Secondary Objectives: to assess levels of BPI and optionally, levels of natural BPI and rBPI21 in pulmonary secretions; to assess the potential effect of rBPI21 on bacteria in the pulmonary secretions; to assess the potential effect of rBPI21 on bacterial LPS and selected inflammatory cytokines in both blood and pulmonary secretions; and to explore potential clinical efficacy endpoints.